Thermal disconnect

Abstract

A drive disconnect device is provided in which input and output shafts are provided in splined engagement. The splines are aligned with the axes of the input and output shafts such that the force acting between the shafts in a separating direction is substantially invariant of the torque being transmitted. The shafts are spring biased to a disengaged position. The biasing force is resisted by a meltable restraining element which is arranged to melt when the temperature exceeds an acceptable value so as to allow the spring to cause the shafts to disengage from one another.

What is claimed is:  
     
       1. A drive disconnect device, comprising: 
       an input element having a first axis and a first connection region carrying first engagement elements;  
       an output element having a second axis and a second connection region carrying second engagement elements;  
       a restraint device; and  
       a biasing arrangement;  
       wherein the input element and output element can undergo relative axial displacement with respect to one another between a coupled position where the first engagement elements cooperate with the se engagement elements such that the input element is drivingly connected to the output element, and a decoupled position where the first and second engagement elements are disengaged from one another, the biasing arrangement acts to urge the input and output elements towards the decoupled position and the restraint device serves to resist the urging of the biasing arrangement until the temperature of the restraint device exceeds a predetermined value, and wherein contacting surfaces of the engagement elements which serve to transmit load between the input element and the output element extend parallel with the axis of the input and output elements.  
     
     
       2. A drive disconnect device as claimed in  claim 1 , in which the first and second engagement elements are splines. 
     
     
       3. A drive disconnect device as claimed in  claim 1 , in which the first engagement elements extend radially outward from the input element and the second engagement elements extend radially inwardly from the output element. 
     
     
       4. A drive disconnect device as claimed in  claim 1 , in which the input element carries a third engagement region for releasably engaging with a drive shaft of a prime mover. 
     
     
       5. A drive disconnect device as claimed in  claim 4 , in which the third engagement region is connected to the drive shaft via coupling element which has a fourth engagement region which drivingly couples with the third engagement region when the input element is coupled to the output element, and the third and fourth engagement regions disengage from one another when the input element decouples from the output element. 
     
     
       6. A drive disconnect device as claimed in  claim 1 , in which the restraint device is formed of a material whose melting temperature is well controlled. 
     
     
       7. A drive disconnect device as claimed in  claim 1 , in which the restraint device is positioned such that it is within a substantially sealed container such that it is restrained from coming into contact with a lubricant used in the vicinity of the drive disconnect device. 
     
     
       8. A drive disconnect device as claimed in  claim 7 , in which the restraining means is in contact with a first side of a wall of the container, a second side of the said wall being in contact with the lubricant. 
     
     
       9. A drive disconnect device, comprising: 
       an input element having a first axis and a fist connection region carrying first engagement elements  
       an output element having a second axis and a second connection region carrying second engagement elements;  
       a restraint device; and  
       a biasing arrangement;  
       wherein the input element and output element can undergo relative axial displacement with respect To one another between a coupled position where the first engagement elements cooperate with the second engagement elements such that the input element is drivingly connected to the output element, and a decoupled position where the first and second engagement elements are disengaged from one another, the biasing arrangement acts to urge the input and output elements toward the decoupled position and the restraint device serves to resist the urging of the biasing arrangement until the temperature of the restraint device exceeds a predetermined value, and wherein the engagement elements are axially extending splines.